This invention relates to biological control of crown gall disease on grapevines as well as enhancing grapevine development.
Crown gall disease of grapevine caused by Agrobacterium vitis is a limiting factor to grape production in several regions of the world (Burr et al. (1999) Annu. Rev. Phytopathol. 37:53-80). A. vitis survives systemically in grapevines and therefore is disseminated in propagation material (Burr et al. (1984) Plant Dis. 68:976-978; Burr and Katz (1983) Phytopathology 73:163-165; Goodman et al. (1987) Am. J. Enol. Vitic 38:189-193). Like crown gall on other plant species, tumorigenesis results following the transfer of a set of oncogenes called the T-DNA that are carried on a bacterial Ti plasmid; the T-DNA becomes integrated and expressed in the plant host (Chilton et al., (1977) Cell 11: 263-271) leading to crown gall. A. vitis strains can be grouped based on the type of Ti plasmid they carry and may also be designated by the opine catabolic gene(s) that resides on their Ti plasmid (Otten et al. (1996) Mol. Plant-Microbe Interact. 9:782-786).
There are no effective chemical controls to combat crown gall and therefore the interest in developing a biological control. Biological control of crown gall on specific crops, such as stone fruits has been successfully implemented in commercial agriculture using A. radiobacter strain K84 (Farrand, (1990) In R. R. Baker, and P. E. Dunn (Eds.) pp. 679-691). K84 is not effective against A. vitis strains on grapevine and therefore several research groups have investigated other candidate biological control strains for crown gall control on grape. Some of the more recent research on biological control of grape crown gall included nontumorigenic A. vitis strain E26 (Liang et al. (1990) Acta Microbio Sin 30:165-171) and strain VAR03-1 (Kawaguchi et al. (2008) Phytopathology 98:1218-1225). Other strains including Rahnella aquatilis strain HX2 (Chen et al. (2007) Plant Disease 91: 957-963), Serratia plymuthica strain IC1270, Pseudomonas fluorescens strain Q8r1-96, P. fluorescens strain B-4117 (Dandurishvili et al. (2010) Journal of Applied Microbiology 110: 341-352) and others were shown to provide various levels of grape crown gall inhibition under experimental conditions (Eastwell et al. (2006) Crop Protection 25:1191-1200).
Accordingly, there is a need in the art for effective controls of crown gall disease on grapevines. The present invention provides such a need.